When President Barack Obama announced on March 31 that he would support expanded offshore oil and natural gas drilling--overturning a decades-long moratorium on new energy exploration--environmentalists warned that he was playing with fire. It didn't take them long to say, Told you so. On April 20, an explosion rocked the Deepwater Horizon oil rig in the Gulf of Mexico, killing 11 workers onboard and leaving the operation crippled. The deaths were tragic enough, but when the rig began to sink on April 22, it opened the door to a new danger: an oil spill that could blanket the Gulf Coast.

On April 24, the Coast Guard reported that more than 40,000 gal. of crude oil a day was leaking into Gulf waters just 50 miles south of the coast of Louisiana. Within days, the spill had produced an oil sheen more than 1,800 sq. mi. large, threatening the sensitive Gulf coastline, home to seabirds and marine mammals along with prime fishing and tourist spots. While the oil is not all that toxic--and will eventually evaporate if it remains in the open sea--tides of crude onshore can foul nesting areas and smother animals. "It could ruin the sensitive bird-breeding areas we've been trying to bring back and restore on the Gulf Coast," says LuAnn White, director of the Tulane Center for Applied Environmental Health.

While Coast Guard officers and officials from energy giant BP, which operated the Deepwater Horizon rig, were still hoping to close the drilling pipe, fears increased that the incident could become a major disaster, comparable to that of the Exxon Valdez, which spilled 11 million gal. of oil in Alaska's pristine Prince William Sound in 1989. "If it keeps going--and that's a big if--the probability gets higher and higher that you could have a major impact on the land," says Nancy Kinner, co-director of the Coastal Response Research Center at the University of New Hampshire.

However serious the Deepwater Horizon oil spill ends up being, the accident provides a timely reminder of how dangerous offshore energy exploration can be. Seawater is corrosive to equipment, and the weather on the high seas can be violently unpredictable; in 1980 a storm in the North Sea capsized a Norwegian oil rig, killing 123. The Gulf incident "raises serious concerns about the industry's claims that their operations and technology are safe enough to put rigs in areas that are environmentally sensitive," wrote a group of Senators in an open letter on April 26. Obama's plan for offshore drilling--widely thought to be a trade to conservatives in exchange for their support for climate-change legislation--might already be sunk. Along with the wreck of the Deepwater Horizon.